Manufacture of arsenious oxid.



Patented Oct. 6, 1908.

U. WEDGE, MANUPAGTURE 0F ABSENIOUSVOXID.

APPLIUATION FILED NOV. 13, 1907.

-l ll errer `or Anunciar.,

'iisra'risiiJ van In.

MANUFAGTURE' oF ARsEiIIoUs oxin.

Specification of Lettera Patent.

Application tiled November 18, 1907. Serial No. 402,015.

To all whom it may concern:

lle it known that I, U'rLnY Wenen, a citizen of the United States,residing in Ardmore, ,Pennsylvanim have invented certain .Improvementsin the Manufacture of Ari This object I attain in the of said apparatus,and Fig. 3 a sectional view illustrating a` modification 'of one of* thefeatures of my invention.

-, The sulfid of arsenic sludge resulting as a waste product in themanufacture of sulfuric aciyd always contains more or less free acid,

and,` in carrying Aout my present invention, l eliminate* this free acidby 'first washing' the sludge with water and then with a solution ofsome alkali, such,`for instance, as

soda ash, `in order to neutralize all traces of freejsulfuric acidremaining therein.' lV hen this has'been :v cconiplisliecl, I thenpartially dry tliersludge, preferably by means of an ordinaryfilterrvpress, which also reduces the sludge to cake form, so that itcan be conveniently handled. fIn this condition, howT ever, it stillcontains about forty per cent. of moisture, and, iu order to bettereffect the subsequent driving off, by heat, of the arsenic vapors orgases (hereinafter, for con venience` termed vapors) this should beremoved. plish b v drying the cakes of sludge al' a temperature not highenough tol vaporize the arsenitl contained in the sludge, say at aboutUlli A\fter it has been thoroughly dried the sludge can bei broken intopieces of any desired size and it will then burn freely in a furnacesuch as is illustrated in my appliration for patent. Serial. No. 32l,$$.tiled Julie t5, 1906, said furnace having a hearth with nllielevntedreceiving member l and a discharging member 2 connected b v an nelinedmember il, said hearth being heated by moisture This result I accom-lproducts ofcon'ibustion circulating beneath it thronvh fines 4, and areverberatory action being olbtained by carrying the same, or

other, products of combustion through a chamber 5 in the hollow roof ofthe furnace.

The sultid 'ofarsenic sludge which results as a waste product ofsulfuric acid manufacture is usually a combination of'the trisuld andthe pentasultid, and, owing to the loosely combined atoms of sulfur inthe lat! ter, free combustion of the dryl sludge, attended by tlieevolution of arseuious oxid vapor and sulfurous acid gas, will takeplace when said sludge is thrown and spread upon the upper member 1 ofthe hearth, and is exosed to the heat thereof and also to the heatradiated from the roof of the furnace.

The sludge can be readily drawn down over the inclined member 3 of thehearth and onto the base member 2 of thejsame. from which it. can beremoved after all of the vapors have been driven ott'. It' a propertemperature is maintained the sludge can be effectively treated on aflat hearth'` the hearth with inclined intermediate member beingpreferred, however, as mort` convenient.

In order to maintain the combustion of theslud e the hearth of thefurnace shrnild be heate to redness, and even in that case a quantity ofyellow arsenic 'willvaporize as such without burning, and tolsecure asnitable product of white arsenic it is necessary to the vapors througha retort, which` as in my aforesaid furnace, consists of a outractedApassage 6 between upper and lower slabs or tiles T and 9 interposedbetween upper and lower flues 10 and 1-1, tl'nfough which heatedproducts of combustion are caused to circulate, the retort being of suchconstruetion that there is no tendency of the combustion gases to leakinto the arsenic vapors nor any tendency of the arsenic. vapors to escape into the heating fl'ues. 'l'he additional heat to which the yellowarsenic vapors are subjected in this retort is sufficient to cause thecombustion of the same, consequently Patented occ. 6,)1908.

ceV

-lOtl only the white arsenic vapors issue from the deliver end of thelretort', the length of tbc retort ',eing such as to insure this action.4These vapors are, however", of ,such a high tem eratuife that ifpermitted to pass direct y intof an ordinary condensing chamber, theywill, in a. short. time, heat to a relatively high degree` the walls ofsaid chamber, al' and near the inlet, and forni strongly ad hei-ing andhard cr stalline masses on saidl walls, instead of diepositing thearsenious oxid upon the floor of this-portion of the chamber in the formof a finely divided powder, as is desired, andv as is effected in thefurther portions of the chamber after the vapors have been partiallycooled.l I find it advisable, therefore, to so conduct the con* densingoperation that the vapois will, at l'the beginning of the o eration bebrought into contact with condensing surfaces so cooled thattlieobjectionable results vabove noted Will be prevented`. In orderto`accomplish this, I preferably pass the heated vapors from the retortacross a chamber 12 provided with depending tubes 13 through which a Howof Water or other cooling agent is maintained in'any suitable'manner thetemperature of the arsenic vapors being thereby properlyreduced beforethey pass through the neck 14 into the condensing chamber 15. t

The chamber 15 is contained, as usual, within ar casing 16 exposed tothe air, and composed of metal, brick, Wood, or other availablematerial, lead being preferred, andv I also .find it preferable torovide such chamber with one or more per orated transverse partitions17, in order to check in some degree the freedom of How of the arsenicvapor through the chamber from the inlet.

A neck 14- to the outlet flue 19.

cooler, the arsenious oxid the 'furnce 'and the condensing chamber,

The coolingdevice interposed 'between the vretort and". the condensingchamber lshould not be such as to cool thea'rsenic vapors to anextent'wliich will. cause precipitation of the arseiiiousj oxid in suchcoolen' It isdesirable, hweger, to cool the vapors so that thetemperature of the sameat "the forward. end of the 'condensing chamberwill not exceed 240"v F When this :rule is observed, little or noarsenic will be recipitat'ed in the lieing precipitated in the chamber15, where it can be easily collected without interruptn the continuedoperation of -fthe ,plant .'Ie condensing chambers should have about twocubic feet` of space per pound of dry sludgevburi'ied in iours.

. -,li'isteadfof using a coolingdevice between ineasurab yqjtrhe saineeffect may, if desired,

Vdie attaiiid .by providing the casing attlie ."'forivai'd or receivingend of said chamber with vpipes or passages, external or internal', forfthe flow of a suitable copliiig agent a water jacket-'2Q beingshown'for this pur- 'posein Fig. 32 By this means the undue heatin ofthe walls of the chamber by contactwith the lhot gases is prevented, andthe objections beforeiioted are overcome.

I donot herein4 claim the inode of recover-I ing arsenious oxid by firstsubjecting fused--` and flowing sulid tothe action of heat and thancooling the evolved gases to .condense evolved gases before coolingthem, as such treatmentforins part of the invention con- 'stit-utin thesubject of my previous applica- 'tion be ore referred to.

I Claim-f A f Tli'e process herein described of recovering arseniousoxid from the sulfid of arvthe saine, oi' the further heating of said Isenic sludge produced in! sulfuric acid manu! facture,'s,a id processconsisting in neutralizing the sludge, tlien drying and burning thesaine,.theii condensing the resulting vapors po deposit" the' oxid, andthen collecting the sitter.

2. In the process of recovering arsenious' oxid from the sulfid 4ofarsenic sludge produced iii sulfuric acid manufacture, the improvementwhich consists in drying the sludge,th en burning the sain'e, thencondensing the resulting vapors to deposit the oxid, and then collectingIthe latter.

L In the process of recovering arsenious oxid from the sulfid of arsenicsludge produced in` sulfuric acid manufacture, the improvement' whichconsists in burning the sludge',tlien condensing the resulting vapors tocause deposit of the oxid, and as a feature of sucli condensingoperation so cooling the )riinry surfaces with whichy the vapors arebrought into contact as to prevent the oxid from adhering thereto, andthen collecting lthe oxid. .f

duced in sulfuricacid manufacture, the improvement which .consistsincalcining the sludge, further heating the resulting vapors, and thencondensing said vapors to cause de posit ofthe oxid, and, as a featureof such condens'y r operation, so cooling the primary surfaces y 'ithwhich the vapors are brought inlo contact tis to prevent the oxid fromad-l.

.oxid from the snltid of arsenic sludge prorlui'ing thereto, and finallycollecting the oxid.

(i. In the process of recovering arsenious f oxid from the sultid ofarsenic sludge pro'- iluf'ed in sulfuric acid manufacture, theiinprovcinent which consists in calcining the sludge, further heatingthe resultant vapors,

partially cooling said vapors, then further cooling the same to depositthe o.\'id,' and llicn collecting, the latter. f

l. Ille process herein described of recovering 'arseniousoxuLifroni thesnltid of arfseine sludge produced in sulfuric acid inanu farli'ire,siiidpizoress @insisting .in .I iru` lralizin the sludge, then dryingthe saine. `then burning said drlecl product, then condensing' theresultingr vaporsr to cause deposit of the oxid, and. as a feature ofsuch condensing operation, so cooling the primary. surfaces with whichthe vapors are brought intotcontact as to prevent the oxid fromadliering,lr thereto. and inallxv collectingr thc oxid.

S. 'lhel process herein described of recovering` arsenious oxid from thcsulfid of arsenic sludge produced in sulfuric acid inanufacture, saidprocess consisting in first ncu tralizing the sludge. then dryingl thesame, then burning said dried product, then partially cooling theresulting vapors, then further cooling said vapors to deposit the oxid,and then collecting the latter.

9. The process herein described of r'ecov-y cring arsenious oxid fromthe `suld of arsenic sludge produced in sulfuric acid manufacture, said`process consisting in first neutralizing, the sludge, then dryingvr thesame, then calcining said dried-product, then subjecting the resultingvapors to further heatfacture, said process consisting in first neuit'ralizing thc sludge, then drying the saine,

`then calcining said dried product, then sub-v jecting the resultingrvapors to further heat.- ing, then partially cooling said vapors, thenfurther coolin the same to depositthe oxid. and finally co lecting vthelatter.

In testimon",r whereof, I have signed my naine to this speciticution,inthe presence of two subscribing witnesses.

UTLm wianou.

'Witnessesz HAMILTON D. TlRNEn,

Kw1-z A. BEADLE.

